Urinary casts are cylindrical structures produced by the kidney and present in the urine in certain disease states. They form in the distal convoluted tubule and collecting ducts of nephrons, then dislodge and pass into the urine, where they can be detected by microscopy.
They form via precipitation of Tamm-Horsfallmucoprotein which is secreted by renal tubule cells, and sometimes also by albumin in conditions of proteinuria. Cast formation is pronounced in environments favoring protein denaturation and precipitation (low flow, concentrated salts, low pH). Tamm-Horsfall protein is particularly susceptible to precipitation in these conditions.
Casts were first described by Henry Bence Jones (1813-1873).
As reflected in their cylindrical form, casts are generated in the small distal convoluted tubules and collecting ducts of the kidney, and generally maintain their shape and composition as they pass through the urinary system. Although the most common forms are benign, others indicate disease. All rely on the inclusion or adhesion of various elements on a mucoprotein base—the hyaline cast. "Cast" itself merely describes the shape, so an adjective is added to describe the composition of the cast. Various casts found in urine sediment may be classified as follows.

This is an excerpt from the article Granular cast from the Wikipedia free encyclopedia. A list of authors is available at Wikipedia.

The article Granular cast at en.wikipedia.org was accessed 114 times in the last 30 days. (as of: 07/20/2013)

Granular cast. This cast (arrows) is composed of a diffuse scattering of fine
granules over its entire surface (bright-field microscopy, X 1 60.) (From the
College of American Pathologists, with permission.) some Granular casts, cell
wall remnants ...

Ricardo H. Bardales Associate Professor of Pathology at the University of Minnesota School of Medicine, 2002

Granular cast. A coarsely Granular cast was present. presence of cellular
degeneration, the distinction of epithelial from white cell casts may be difficult and
ultimately, like white cell casts, they may become nonpigmented Granular casts (
Fig.

In this article, we are going to discuss the interpretation and significance of the data found in a urine analysis report regarding the microscopic examination of urine sample which includes the Pus cells, R.B.Cs, casts and urine crystals .

Granular casts are the second-most common type of cast and they are the result either from the breakdown of cellular casts or the inclusion of aggregates of plasma proteins or immunoglobulin light chains. Depending on the size of inclusions, Granular casts can be classified as fine or coarse, though the distinction has no diagnostic significance.

Hyaline castsHyaline casts are formed in the absence of cells in the tubular lumen. They consist of Tamm-Horsfall protein and have a smooth texture and a refractive index very close to that of the surrounding fluid.

http://cgi.ebay.com/B-D-Dukoff-Hollywood-tenor-mouthpiece-/180526421936?cmd=ViewItem&pt=LH_DefaultDomain_146&hash=item2a083697b0
..And here is another fake casting of a B.D. Hollywood tenor piece. It is called an "oddball" DUkoff, and has been refaced by BP, but is actually a fake, probably sandcasting and not at all an original blank. Notice the little holes all over the surface metal. In this case this is not pitting from age, but original due to the Granular casting surface.